Catheterization method using proximal articulation and pre-formed distal end

ABSTRACT

Methods of using a catheter involve providing a sheath comprising a proximal region, a deflection region, a distal-end region including a shapeable region, an anchor region defined between the deflection region and the shapeable region, and a longitudinal axis. The method also involves imparting a pre-established shape to the shapeable region. The method further involves applying axial force in a proximal direction at the anchor region so as to cause the deflection region to deflect relative to the longitudinal axis while the pre-established shape imparted to the shapeable region of the sheath is substantially maintained.

RELATED PATENT DOCUMENTS

This application is a divisional of U.S. patent application Ser. No.10/105,087, filed on Mar. 22, 2002, now U.S. Pat. No. 6,869,414, towhich priority is claimed under 35 U.S.C. § 120, and which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to steerable catheters and, moreparticularly, to methods involving a steerable catheter employing apre-formed distal end section and a proximal steering mechanism.

BACKGROUND OF THE INVENTION

Mapping and ablation catheters are well-established technologies thatallow the physician to locate and treat damaged cardiac tissue.Presently, a considerable amount of time is often spent by the physicianwhen manipulating such catheters within cardiac structures, such as theright atrium, simply trying to locate an anatomical feature of interest,such as the coronary sinus ostium.

A pre-shaped guiding catheter is typically used to blindly locate thecoronary sinus ostium, but this endeavor is complicated by the fact thatthe location of the coronary sinus ostium may vary appreciably from onepatient to another, especially among patients with diseased hearts.Oftentimes, the clinician is entirely unable to locate the coronarysinus ostium using the guiding catheter, and must resort to finding theostium by “mapping” (interpreting localized bipolar waveforms) using anelectrophysiological (EP) catheter and an ECG monitor. After the ostiumis located, a guiding catheter or sheath is typically used to injectradiographic contrast media into the coronary sinus to highlight theassociated venous system, and then a pacing lead is installed within oneof the coronary branches.

Steerability is also important for ablation catheter implementations. Inmany cases, ablation of the damaged tissue can restore the correctoperation of the heart. Ablation can be performed, for example, bypercutaneous ablation, a procedure in which a catheter is percutaneouslyintroduced into the patient and directed through an artery to the atriumor ventricle of the heart to perform single or multiple diagnostic,therapeutic, and/or surgical procedures. In such a case, an ablationprocedure is used to destroy the tissue causing the arrhythmia in anattempt to remove the electrical signal irregularities or create aconductive tissue block to restore normal heartbeat or at least animproved heartbeat. Successful ablation of the conductive tissue at thearrhythmia initiation site usually terminates the arrhythmia or at leastmoderates the heart rhythm to acceptable levels. A widely acceptedtreatment for arrhythmia involves the application of radio frequency(RF) energy to the conductive tissue.

By way of example, a procedure to address atrial fibrillation, referredto as Cox's Maze procedure, involves the development of continuousatrial incisions to prevent atrial re-entry and to allow sinus impulsesto activate the entire myocardium. While this procedure has been foundto be successful, it involves an intensely invasive approach. It is moredesirable to accomplish the same result as the Maze procedure by use ofa less invasive approach, such as through the use of an appropriateelectrophysiological (EP) catheter system having enhanced steering andshape adjustment capabilities.

Steerable conventional mapping and ablation catheter systems aretypically configured to allow the profile of the distal end of thecatheter to be manipulated from a location outside the patient's body.The contours of pre-shaped diagnostic catheters, for example, aregenerally fixed, and this is typically achieved in production byconstraining the distal end within a shaping fixture while warming themuntil they assume the intended shape (i.e., by “heat setting” theirpolymer shaft). The shape of steerable mapping catheters, on the otherhand, can be altered by the user simply by applying tension to one ormore internal steering tendons affixed to a distal-end tip of thecatheter. However, most steerable mapping catheters are generallystraight when no tension is applied to the tendons. When steered, thedistal end of such steerable catheters assumes a semicircular arc orfull circular shape whose radius of curvature depends upon the amount oftension applied to the steering tendon.

FIGS. 1 and 2 illustrate a conventional steerable catheter in a relaxedconfiguration and a steered configuration, respectively. Catheter 20 isshown to include a number of band electrodes 22 and a tip electrode 24.As can be seen in FIG. 1, catheter 20 maintains a relatively straightprofile while in a relaxed configuration.

FIG. 2 illustrates the catheter 20 of FIG. 1 in a steered configuration.According to this and other conventional steerable catheterimplementations, catheter 20 has a distal end that assumes asemicircular arc or a fully circular shape when tension is applied tothe catheter's steering tendon(s). The circular arc of catheter 20, whenin its steered configuration, develops a shape whose radius, R, ofcurvature depends upon the amount of tension applied to the distal endvis-à-vis the steering tendon(s). It will be appreciated by thoseskilled in the art that enhanced steering capabilities are oftenrequired over and above those offered by conventional steerablecatheters, such as those of the type depicted in FIGS. 1 and 2, forlocating (e.g., such as by mapping) certain anatomical features andperforming an ablation technique once such anatomical features have beenlocated and accessed.

There is a need for an improved steerable catheter having enhancedsteering capabilities for mapping and ablation applications. Thereexists a further need for such a catheter that provides for increasedlumen space for accommodating larger payloads and one that resistsdeformation after repeated steering. The present invention fulfillsthese and other needs, and addresses other deficiencies of prior artimplementations.

SUMMARY OF THE INVENTION

The present invention is directed to methods involving manipulation of acatheter or sheath. According to one embodiment, a method involvesproviding a catheter comprising a proximal region, a pre-formed regionat a distal end of the catheter, a deflection mechanism proximal to thepre-formed region, a deflection region proximal to the deflectionmechanism, and a longitudinal axis. The method also involves applyingaxial force in a proximal direction to the deflection mechanism, theaxial force causing the deflection region to deflect relative to alongitudinal axis of the proximal region of the catheter while apre-formed shape of the pre-formed region is substantially maintained.The method further involves resisting axial compression along thelongitudinal axis at the deflection region resulting from application ofthe axial force.

According to another embodiment, a method involves providing a sheathcomprising a proximal region, a deflection region, a distal-end regionincluding a shapeable region, an anchor region defined between thedeflection region and the shapeable region, and a longitudinal axis. Themethod also involves imparting a pre-established shape to the shapeableregion. The method further involves applying axial force in a proximaldirection at the anchor region so as to cause the deflection region todeflect relative to the longitudinal axis while the pre-establishedshape imparted to the shapeable region of the sheath is substantiallymaintained.

The above summary of the present invention is not intended to describeeach embodiment or every implementation of the present invention.Advantages and attainments, together with a more complete understandingof the invention, will become apparent and appreciated by referring tothe following detailed description and claims taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of a catheter employing a prior art steeringmechanism, the catheter shown in a relaxed configuration;

FIG. 2 is a depiction of the catheter of FIG. 1 shown in a steeredconfiguration;

FIG. 3A is a depiction of a catheter employing a proximal steeringmechanism and pre-shaped distal end in accordance with an embodiment ofthe present invention, the catheter shown in a relaxed configuration;

FIG. 3B is a depiction of a catheter employing a proximal steeringmechanism and looped pre-shaped distal end in accordance with anotherembodiment of the present invention, the catheter shown in a relaxedconfiguration;

FIG. 4A is a depiction of the catheter of FIG. 3A shown in severalsteered configurations;

FIG. 4B is a depiction of the catheter of FIG. 3B shown in severalsteered configurations;

FIG. 5 is a depiction of a catheter employing a proximal steeringmechanism and pre-shaped distal end in accordance with an embodiment ofthe present invention;

FIG. 6A is a cross-sectional view of a catheter employing a proximalsteering mechanism in accordance with an embodiment of the presentinvention;

FIG. 6B is a cross-sectional view of the catheter shaft subassembly at aproximal section of the catheter shown in FIG. 6A;

FIG. 6C is a cross-sectional view of the catheter shaft subassembly ofthe catheter depicted in FIG. 6A taken at a deflection region situatedbetween the proximal section and an anchor section of the catheter shownin FIG. 6A;

FIG. 7A is a side view of the anchor section of the catheter shown inFIG. 6A;

FIG. 7B is a cross-sectional view of the anchor section of the cathetershown in FIG. 6A;

FIG. 8A is a more detailed cross-sectional view of a proximal section ofthe catheter shown in FIG. 6A according to an embodiment of the presentinvention;

FIG. 8B is a more detailed cross-sectional view of the anchor section ofthe catheter shown in FIG. 6A according to an embodiment of the presentinvention;

FIG. 9A is a view of a support system comprising a flat-wired coil andstruts;

FIG. 9B is a view of a support system comprising a round-wire coil andstruts;

FIG. 9C is a view of a support system comprising a tubular member withan array of deep notches;

FIG. 9D is a perspective view of the support system shown in FIG. 9C;and

FIG. 9E is a view of a support system comprising a linear array ofhollow rings connected with struts.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail hereinbelow. It is to beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the invention isintended to cover all modifications, equivalents, and alternativesfalling within the scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

In the following description of the illustrated embodiments, referencesare made to the accompanying drawings which form a part hereof, and inwhich is shown by way of illustration, various embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized, and structural and functional changes maybe made without departing from the scope of the present invention.

Referring now to the drawings, and in particular to FIG. 3A, there isillustrated a catheter implemented in accordance with an embodiment ofthe present invention. The catheter 40 advantageously employs apre-shaped distal section in combination with a deflectable proximalsection which advantageously provides for controlled articulation of thecatheter 40 without significantly altering the distal section'spredetermined shape. In accordance with this embodiment, catheter 40 isshown to include a pre-shaped section 44 extending from a distal tip 46of the catheter 40 toward a deflection section 48. The deflectionsection 48 provides for controlled articulation of the pre-shapedsection 44 and distal tip 46 for steering the catheter 40 throughvasculature and cardiac structures and for dynamically adjusting theoverall contour of the catheter 40 during use. The pre-shaped section 44and distal tip 46 are preferably formed of a resilient material suchthat the pre-formed shape of the various catheter sections caneffectively be straightened when the catheter 40 is inserted into apatient's vasculature or other constraining tissue structure.

A catheter 40 implemented in accordance with the present invention maybe used in many applications, such as in mapping or ablationapplications. If catheter 40 is equipped with thermal sensors, forexample, catheter 40 can be used to generate long, continuous lesionsfor the treatment of atrial fibrillation or atrial flutter.

An articulating catheter 40 in accordance with the present invention maybe implemented in a variety of forms, such as in the form of anelectrophysiological (EP) mapping catheter having multiple bandelectrodes 42. The band electrodes 42 disposed at the distal-end regionof catheter 40 are used to collect localized ECG signals for thespecialized purpose of locating the coronary sinus. It is readilyappreciated by those skilled in the art that the articulating catheterof the present invention can also be used to deliver radio frequency(RF) energy to locally ablate cardiac tissue and thereby alter itsinherent electrical conduction.

By way of further example, an articulating catheter 40 employing apre-shaped distal section 44 and deflectable proximal section 48 may beused within the right atrium for mapping purposes to positively locatethe ostium of the coronary sinus. It is well understood in the art thatthis activity is known to be particularly challenging within heartswhere the anatomy has been distorted by chronic disease, such ascongestive heart failure (CHF) or atrial fibrillation (AF). It isnecessary, for example, to specifically locate the coronary sinus whenimplanting one of the pacemaker leads for synchronized dual-chamberpacing CHF patients. A shape-adjustable catheter implemented accordingto the principles of the present invention can be used to efficientlylocate the coronary sinus and other anatomical features of interest.

In accordance with a further illustrative example, an alternate distalconfiguration of the catheter 40 is illustrated in FIG. 3B. Thecombination of a pre-shaped distal portion 44 and a deflectable proximalsection 48 implemented in catheter 40 may be useful within the leftatrium for accurately positioning an array of ablation electrodes aroundthe ostia of one or more of the pulmonary veins in order to producebi-directional conduction block. It is considered necessary to createsuch block often when treating AF patients using RF ablation toless-invasively emulate the established open heart surgical procedurecommonly known as Cox's Maze procedure.

The pre-shaped distal portion 44 in the configuration of FIG. 3Bincludes a substantially circular or semi-circular loop. The bandelectrodes 42 deployed at the pre-shaped distal portion are therebyarrayed in a shape that is particularly suited for creating a conductionblock in one or more pulmonary veins.

An important advantage provided by an articulating catheter 40implemented in accordance with the principles of the present inventionconcerns a significantly increased lumen space within the catheter 40which facilitates an increased number of electrical conductors and othercatheter elements housed within the catheter 40 in comparison to priorart implementations. By way of example, a catheter 40 configured forablation applications in accordance with the present invention mayemploy numerous band electrodes 42 (e.g., 6 or 12 electrodes), eachbearing several individually insulated wires for power delivery andtemperature measurement. In one such configuration, catheter 40 providessufficient lumen space to accommodate numerous electrical wires (e.g.,typically between 15-30 wires), a pre-shaped member situated at thedistal section of catheter 40, two tendon wires, a steering ribbon, andan anchor band, all while maintaining a catheter outer diameter of 7French (2.3 mm). Those skilled in the art will readily appreciate thatproviding sufficient lumen space for such payload presents a significantdesign challenge, which is solved by implementing a catheter 40consistent with the principles of the present invention.

Returning to the discussion of FIGS. 3A and 4A, FIG. 3A illustrates anembodiment of catheter 40 in a relaxed configuration. As is depicted inFIG. 3A, the configuration of catheter 40 in a relaxed state issignificantly different from the relaxed configuration of prior artcatheter 20 depicted in FIG. 1.

FIG. 4A depicts catheter 40 in several steered configurations. Forexample, the pre-shaped section 44 may be selectively deflected from itsrelaxed orientation, O_(R), about a pivot point defined by proximaldeflection section 48. Pre-shaped section 44 may, for example, bedeflected about proximal deflection section 48 in a direction toward thelongitudinal axis of the proximal section of catheter 40, as is depictedat steered orientation, O₁. Also, the pre-shaped section 44 may bedeflected toward and beyond a plane normal to the longitudinal axis ofthe proximal section of catheter 40, as is depicted at steeredorientation, O₂.

By way of further example, FIG. 4B shows steered configurations for anarticulated catheter 40 having a distal loop as seen in FIG. 3B. O_(R)is a relaxed orientation, and O₁ and O₂ are deflected orientationssimilar to those orientations described with respect to FIG. 4A.

As can clearly be seen in FIGS. 4A and 4B, the distal portion ofcatheter 40 may be deflected at selected deflection angles relative toproximal deflection section 48 without significantly altering thepredetermined shape of the distal section of catheter 40. In contrast,the steered configuration of prior art catheter 20 depicted in FIG. 2illustrates significant alteration of the distal section of prior artcatheter 20 in response to deflection forces exerted at the distal end24 of catheter 20.

FIG. 5 is an illustration of an embodiment of the present invention inwhich an anchor region, R_(anch), is shown to be located distal to adeflection region, R_(defl), and proximal to a pre-shaped region,R_(shp). A steering mechanism 56 extends from a proximal section 43 ofcatheter 40 to an anchor band 52 located at the anchor region, R_(anch).A pre-shaped member 54 extends from the anchor band 52 through thepre-shaped region, R_(shp). Preferably, pre-shaped member 54 is securedat the distal tip 46 of catheter 40. By appropriately actuating steeringmechanism 56, tensile and torquing forces are imparted to anchor band 52to cause pre-shaped region, R_(shp), to deflect about the deflectionregion, R_(defl), as will be discussed in greater detail hereinbelow.

The pre-shaped region, R_(shp), takes on a shape consistent with that ofpre-shaped member 54. The pre-formed shape of the pre-shaped region,R_(shp), may have any form which generally conforms to the contour ofthe anatomical feature of interest. For example, the pre-shaped member54 may have a contour that conforms to a biological cavity containingtissue to be ablated. It is understood that the configuration ofpre-shaped region, R_(shp), has been simplified for purposes of clarity,and that pre-shaped region, R_(shp), may take various simple and complexforms. For example, the substantially straight portion of the pre-shapedregion, R_(shp), may instead have a simple or complex curved contourthat follows that of pre-shaped member 54. The pre-shaped section,R_(shp), may, for example, have a form that facilitates treatment ofatrial fibrillation in that its shape allows for the distal portion ofcatheter 40 to be easily inserted into the atrium of the heart. Thepre-formed member 54 employed in combination with proximal deflectionregion, R_(defl), and steering mechanism 56 provides for ashape-adjustable, steerable distal catheter region having a contourwhich may be dynamically adjusted during use to conform to the contourof the atrium or other anatomical feature of interest.

Turning now to FIG. 6, there is illustrated an embodiment of ashape-adjustable catheter 40 employing a proximal steering mechanism inaccordance with the principles of the present invention. It is notedthat the catheter 40 shown in FIG. 6 is depicted in a linear or straightschematic configuration, without curvature indicated for purposes ofclarity. According to this embodiment, catheter 40 is shown to include aproximal section 43, a deflection section 48, a pre-shaped section 44,and a distal tip 46. The shaft of catheter 40 at the proximal section 43includes three layers. An outer layer 60 at the proximal section 43 isformed of a high durometer (e.g., 63 Shore D) PEBAX outer jacket havingan outside diameter of 0.094 inches or 7 French, and an inside diameterof 0.062 inches. The proximal portion 43 of the sheath of catheter 40further includes a braid layer 62 formed of eight strands of interwovenstainless steel ribbon, each with 0.001 inch by 0.003 inchcross-section. The braided ribbon 62 has a diameter of 0.009 inches. Thebraided ribbon 62 stiffens the proximal portion 43 of the cathetershaft, so it minimally deflects under normal steering loads. An innercore of the catheter sheath includes a tube 60 of polyetheretherketone(PEEK), having a diameter of 0.064 inches and an outer diameter of 0.078inches.

At the distal end of the proximal shaft section 43 resides a flexiblecompression cage 120 that engages with the PEEK tube 64 and is embeddedwithin low durometer (e.g., 35 Shore D) PEBAX 60 a. The compression cage120 is preferably formed from nitinol. The sheath section of catheter 40that includes the compression cage 120 and low durometer PEBAX jacket 60a defines all or a substantial portion of the deflection region 48 ofcatheter 40. The combination of compression cage 120 and low durometerPEBAX jacket 60 a provides for deflection of catheter 40 proximal to ananchor band 52 when tension is applied to a steering tendon connected toanchor band 52. The compression cage 120, as will be described ingreater detail below, facilitates deflection of the steering portion ofcatheter 40 relative to a longitudinal axis of catheter 40, and resistsaxial compression along the catheter's longitudinal axis.

To vary the stiffness of the catheter 40, the bending properties ofeither the catheter shaft (e.g., durometer of the polymeric materials)or the pre-shaped section 44 (e.g., the diameter or cross-section of apre-formed stylet) can be varied along its length. This could be done totune the relative stiffness of the distal tip region in order tominimize the risk of trauma. Furthermore, to help the distal tip 46 stayin the coronary sinus while the sheath is slid forward, the pre-shapedsection 44 can include a slight bend or “hook” near the distal tip 46 sothat the catheter 40 is less likely to slip out of the ostium.

As is further shown in FIG. 6A, an anchor band 52 is installed within atleast a portion of the distal of opening of the compression cage 120. Inone configuration, one or two stainless steel tendon wires 76, best seenin FIGS. 8A and 8B, are pre-affixed to the anchor band 52 prior toinstallation. One or two steering tendons 76 can be provided dependingon whether the catheter 40 will steer in a uni-directional orbi-directional manner. Each steering tendon 76 is substantially enclosedwithin a lubricious tendon sheath 77, e.g., PTFE or similar material,that primarily serves to minimize friction between the tendon wire 76and inner catheter wall. In one configuration, the tendon sheath 77 isbonded or otherwise affixed to the inner catheter wall, and the steeringtendon 76 is slidably disposed within the tendon sheath 77. This servesto restrain the steering tendon 76 from undesired movements (e.g. radialdeflections) while allowing the steering tendon 76 to axially slidewithin the catheter's sheath. In an alternate configuration, the tendonsheath 76 can be formed as a void in the PEEK tube wall.

It is preferable that the attachment point of the steering tendon(s) 76to the metallic anchor band 52 be accomplished by welding or soldering.The anchor band 52 may then be embedded within the wall of the catheterduring shaft lay-up. Alternatively, the anchor band 52 may be adhered ata later fabrication stage to the inner wall of the catheter shaft, suchas by adhesive bonding or by hot melting the shaft material.

Attached to a distal end of the anchor band 52 is a hollow distal jacketsection 60 b formed of a low durometer PEBAX material, upon which anarray of band electrodes (not shown) can be placed. The distal tip 46 ofcatheter 40 is typically a metal component that is affixed to the distalend of the PEBAX distal jacket 60 b. The metal component at the distalend 46 of catheter 40 can be platinum, if used for ablation, or lessexpensive stainless steel, if no ablation is intended.

In one embodiment, the electrodes provided at the distal end of catheter40 include twelve band electrodes arranged in a substantially lineararray along the distal portion of catheter 40. A tip electrode may alsobe provided at the distal tip 46 of catheter 40. The band electrodes maybe arranged so that there is space between the adjacent electrodes. Inone configuration, the width of the band electrodes is 3 mm and thespace between the electrodes is 4 mm. It is understood that thearrangement of band electrodes is not limited to a linear array and maytake the form of other patterns. For example, a substantially lineararray is preferred for certain therapeutic procedures, such as treatmentof atrial fibrillation, in which linear lesions of typically 4-8 cm inlength are desired. A linear array is more easily carried by thecatheter 40 and also lessens the size of the catheter.

Temperature sensors for monitoring the temperature of the electrodes atvarious points along the distal portion of catheter 40 may also beprovided. In one configuration, each band electrode has a temperaturesensor mounted to it. Each temperature sensor provides a temperaturesignal which is indicative of the temperature of the respective bandelectrode at that sensor. In another embodiment, a temperature sensor ismounted on every other band electrode. In yet another configuration,every other electrode can have two temperature sensors.

The pre-shaped member 74 is formed of a resilient material capable ofretaining a pre-formed shape upon removal of deformation forces actingthereon. The pre-shaped member 74 is preferably made of superelasticwire or ribbon material so that it readily straightens while being fedinto the cardiac anatomy and then readily resumes its originalpre-shaped configuration. In general, the configuration of pre-shapedmember 74 is selected to approximate a given anatomical requirement. Inaddition, once the pre-shaped member 74 passes into a biological tissuecavity, such as the right atrium, for example, the shape of the distalportion of catheter 40 resumes its pre-formed configuration.

In the configuration illustrated in FIG. 6A, pre-shaped member 74represents a stylet that resides within the catheter 40, and ispreferably affixed to the distal tip 46 of catheter 40 to preventmigration of pre-shaped member 74 within the catheter 40 while in use.The pre-shaped member 74 may also be fixably attached to the anchor band52 by means such as filling the anchor band 52 with an adhesive to trapthe pre-shaped member therein. Attaching the pre-shaped member 74 inthis way allows more effective torque transmission from the catheter'sproximal shaft to the distal tip 46. It is noted that the desiredpre-shape of the distal-end portion of catheter 40 may alternatively beimparted by heat-setting the polymer catheter shaft material at thedistal end of catheter 40.

In one embodiment, pre-shaped member 74 is formed from superelasticnitinol wire which has been previously heated under constraint topermanently set the intended shape. The superelastic nitinol member,such as a stylet, is held in a fixture and heated to approximately 500°C. for about 15 minutes. The diameter of the nitinol stylet can bevaried, such as by grinding, to tailor its bending stiffness whereappropriate, such as to soften the distal tip section for minimizingtrauma risk.

For simplicity, a pre-shaped stylet 74 can have a round cross-sectionover most of its length. In principle, however, pre-shaped stylet 74could have other cross-section, such as a D-shaped, square orrectangular, or other shape depending largely upon the intendedpre-shape and its desired bending characteristics. The pre-shaped stylet74 can also be flattened or tapered where the stylet's proximal portionforms a joint with steering ribbon 70. It is appreciated that a singlepre-shape will likely not be suitable for all patients. Therefore, it islikely that a family of several different pre-shaped stylets 74 would beavailable to the physician.

The steering ribbon 70 extends through at least of portion of theproximal section 43 and substantially all of the deflection section 48of the catheter shaft. The width of steering ribbon 70 is preferablymatched to that of the shaft lumen. As is best seen in FIGS. 8A and 8B,steering ribbon 70 has a width such that it contacts diametricallyopposed sides of the sheath inner wall, thereby bisecting the lumen ofthe proximal and deflection sections 43, 48 of catheter 40. Sets ofelectrical wires 72A, 72B and are separated from one another by steeringribbon 70. An equal number of electrical wires 72 are preferablysituated on either side of steering ribbon 70.

A pair of steering tendons 76, as is further shown in FIGS. 8A and 8B,is separated within the catheter's lumen by steering ribbon 70. In theproximal section 43 of the catheter's lumen, steering tendon(s) 76 arecovered with a tendon sheath 77, such as by a coating of PTFE. It isnoted that the steering tendon wire(s) 76 are not sheathed in theparticular cross-section shown in FIG. 8B because the tendon(s) 76 arewelded directly to the inner wall of the anchor band 52.

The steering ribbon 70 not only conveniently segregates the electricalwires, but it also forces the steering tendon(s) 76 to always residealong the same side as their attachment point(s) on the anchor band 52.If the later were not so, then it would be possible for the deflectablesection 48 to deflect in an unintended direction or assume anunpredictable profile, such as the shape of the “S,” instead of asemicircular arc or other shape that is intended. It is noted that ifthe steering ribbon 70 were eliminated, then steering profiles could becontrolled by permanently affixing each steering tendon sheath 77 to theinner wall of the shaft lumen in order to prevent tendon wire migration.As shown, the steering ribbon 70 is deliberately thin for ease ofbending, and preferably made of a resilient material, such assuperelastic nitinol, so that it can withstand severe deflections due tosteering without permanently deforming.

As is shown in FIGS. 6A and 8B, a proximal end portion of pre-shapedmember 74 is joined with a distal-end portion of steering ribbon 70within anchor band 52. As shown in FIGS. 6A and 8B, a lap joint betweenthe steering ribbon 70 and pre-shaped member 74 is formed within theanchor band 52.

The anchor band 52 can be formed from a stainless steel ring, and istypically affixed to the shaft wall material 60 of catheter 40. Side andfront views of anchor band 52 are provided in FIGS. 7A and 7B. Anchorband 52 includes a main cylindrical portion 55 and a number of spacedannular rings or ribs 53. The anchor band 52 may also include one ormore weep holes 57 that allow filling the anchor band with an adhesiveduring assembly. The steering tendon wire(s) 76 is preferably welded orsoldered to the inner wall of the anchor band 52. The steering tendonaxis is parallel to but offset from the longitudinal axis of thecatheter shaft. Pulling the steering tendon 76 causes the shaft todeflect such that the pulled tendon 76 always follows the inside radiusof shaft curvature.

To improve torque transmission of the overall catheter assembly, theremaining space within the anchor band 52 may be filled with an adhesiveor other filler material, such as epoxy, cyanoacrylate, urethane, orother suitable filler material. Use of such an adhesive as a fillermaterial within anchor band 52 also serves to maintain alignment betweenthe preferred bending planes of the compression cage 120 and steeringribbon 70, thereby assuring steering uniformity.

The deflectable section 48 of catheter 40 is advantageously implementedto deflect in a predictable, selectable manner, while carrying theaccompanying axial compressive load whenever a tensile load is appliedto a steering tendon 76. Those skilled in the art readily appreciate thedifficulty for an ordinary thin-wall deflectable structure to enduredeformation forces associated with catheter manipulation withoutbuckling or excessively wrinkling. Catheter 40 implemented in accordancewith an embodiment of the present invention employs a compression cage120 that allows for a desired level of catheter shaft flexibility at thedeflection section 48 of catheter 40, while providing the requisitecolumnar support needed to prevent undesirable buckling due to excessivecompressive axial loads.

Turning now to FIGS. 9A-9E, there are illustrated various embodiments ofa compression cage 120 in accordance with the principles of the presentinvention. It is understood that a catheter 40 implemented in accordancewith the present invention preferably incorporates compression cage 120within the catheter structure, but in certain implementations,compression cage 120 may optionally be excluded.

With reference to FIGS. 9A-9E, various configurations of a supportsystem or compression cage 120 are shown. In one configuration, shown inFIG. 9A, the compression cage 120 includes a flat-wire coil 126 and twosubstantially longitudinal struts 128. The struts 128 are diametricallyopposed from each other and are welded, soldered, brazed, adhered, orotherwise attached to some or all loops of the coil 126. In anotherconfiguration, shown in FIG. 9B, the compression cage 120 includes around-wire coil 130 and two substantially longitudinal struts 132. Thestruts 132 are diametrically opposed from each other and are welded,soldered, brazed, adhered, or otherwise attached to some or all loops ofthe coil 130.

In another configuration, shown in FIGS. 9C and 9D, the compression cage120 includes a substantially tubular member 134 with an array of deepnotches 136 cut at a pitch angle. The material remaining betweenopposing notches 136 is thereby formed into a substantially helicalstructure with connecting struts 138. In yet another configuration,shown in FIG. 9E, the compression cage 120 includes a linear array ofrings 140 and two substantially longitudinal struts 142 thatinterconnect the rings. The struts 142 are diametrically opposed fromeach other and are welded, soldered, brazed, adhered, or otherwiseattached to each of the rings 140.

The primary function of the struts 128, 132, 138, 142 is to providecolumnar strength to the compression cage 120. When a tensile load isapplied to a steering tendon 76 to induce deflection of the distal-endregion 44 of catheter 40, the reaction to the load is carried by thestruts 128, 132, 138, 142 within the compression cage 120 andtransferred into the relatively rigid proximal region 43 of catheter 40.The compression cage 120 deflects laterally most easily in a directionthat is perpendicular to the plane in which a pair of opposing struts128, 132, 138, 142 are located.

The support system 120 and anchor band 52 can be attached to the innersurface of the sheath within the deflection region 48, such as bymelt-bonding, use of adhesives, or some other mechanical means. In analternate and particularly useful configuration, the support system 120is embedded within the walls of the sheath. Embedding the support system120 within the catheter sheath serves to maximize the lumen diameterbecause there is only one “composite” wall having reduced thicknessrelative to the combined thickness that would result if the supportsystem 120 were attached to an inner surface of the sheath walls.

The proximal end of the embedded support system 120 can be attached tothe catheter using a union 146, best seen in FIG. 9C. An enlarged end ofthe union 146 fits over the distal end of the PEEK tube 64, and thenarrowed end of the union 146 fits inside the support structure 120. Theunion 146 helps ensure that axial compressive loads carried by thesupport structure are reliably transferred to the proximal region 43 ofthe catheter sheath.

A tensile load produced by axial translation of a steering tendon 76 inthe proximal direction causes the deflection region 48 to compress inthe area of the support system 120 and to stretch in the area distal thesupport system 120. However, as previously mentioned, the reaction tothe tensile load is carried by the struts 128, 132, 138, 142 within thesupport system 120 and is transferred into the relatively rigid proximalregion 43 of the catheter sheath, thereby minimizing the associatedcompression and stretching of the deflection region 48 of the cathetersheath.

The support system 120 and other elements of catheter 40 describedhereinabove may be configured as described in commonly owned U.S. Pat.Nos. 6,270,496; 6,585,718; 6,605,086; and 6,096,036, all of which arehereby incorporated herein by reference in their respective entireties.

As was discussed previously, a catheter 40 of the present invention maybe employed in a variety of applications. In a configuration in whichcatheter 40 is implemented as an EP diagnostic catheter, catheter 40 istypically fed through a guiding catheter or introducer sheath and placedwithin the right atrium. The electrical leads from mapping electrodeslocated at the distal-end region of catheter 30 can be connected to anECG monitor, and the ECG waveforms from adjacent electrode pairs can maybe examined. Since the proportion of atrial (“A”) signal relative toventricular (“V”) signal changes progressively throughout the atrium,ECG waveforms can be used to home in on the location of the coronarysinus ostium. It is noted that the coronary sinus resides in a regionwhere the “A” and “V” signals are approximately equal in strength. Usingboth ECG and fluoroscopy feedback, the distal end of the EP diagnosticcatheter 40 of the present invention would be readily manipulated intothe coronary sinus, and then the guiding catheter or sheath would bemade to track over the EP diagnostic catheter 40 and “deep seated”within the coronary sinus. If the sheath were equipped with an occlusionballoon, it could then be inflated to anchor it in place while the EPdiagnostic catheter 40 is removed. At this point, an angiogram wouldtypically be performed followed by implantation of a pacing lead.

An important advantage associated with the present invention is that CHFimplant procedure times presently vary widely, and that an EP diagnosticcatheter 40 of the present invention could be used as a “frontline”device to make the procedure more predictable. Instead of the presentsituation where the clinician is left to his own devices if thepre-shaped guide or sheath fails to locate the coronary sinus, thecatheter 40 of the present invention in conjunction with a non-shapedguide or sheath would provide a consistent, reliable means of quicklylocating the coronary sinus.

In another configuration, a catheter 40 according to the presentinvention can be employed as an ablation catheter. A particularly usefulablation treatment for patients with atrial fibrillation involvesablating tissue around a pulmonary vein orifice. This procedure, knownas circumferential RF ablation, can be used to isolate the pulmonaryveins from the left atrium. The procedure involves introducing theablation catheter 40 into the left atrium, typically via transseptalcatheterization. Proper catheter location within the left atrium can beconfirmed by fluoroscopy or advanced ultrasonic means. Ablation ispreferably performed by applying a combination of bipolar (bandelectrode to band electrode) and unipolar (band electrode to backplate,e.g., cutaneous ground patch) potential differences. These potentialdifferences can be applied using multiphase RF energy delivery as wellas sequential unipolar/bipolar RF delivery. The resulting unipolar andbipolar currents promote both lesion depth and lesion fill-in betweenband electrodes.

It will, of course, be understood that various modifications andadditions can be made to the preferred embodiments discussed hereinabovewithout departing from the scope of the present invention. Accordingly,the scope of the present invention should not be limited by theparticular embodiments described above, but should be defined only bythe claims set forth below and equivalents thereof.

1. A method, comprising: providing a sheath comprising: a proximalregion having a stiffening braid; a deflection region adjacent to theproximal region and distal relative to the proximal region; and adistal-end region adjacent to the deflection region and distal relativeto the deflection region, the distal-end region comprising: a shapeableregion; an anchor region defined between the deflection region and theshapeable region; an anchor band within the anchor region; one or moresteering tendons attached to the anchor band; a compression cagedefining at least a substantial portion of the deflection region, thecompression cage including a coil and two diametrically opposedlongitudinal struts attached to loops of the coil; and a longitudinalaxis; imparting a pre-established shape to the shapeable region; andapplying axial force in a proximal direction at the anchor region usingthe one or more steering tendons so as to cause the deflection region todeflect relative to the longitudinal axis while the pre-establishedshape imparted to the shapeable region of the sheath is substantiallymaintained, wherein the deflection region deflects laterally in adirection that is perpendicular with respect to a projected plane formedby the two diametrically opposed longitudinal struts of the compressioncage.
 2. The method of claim 1, further comprising resisting axialcompression along the longitudinal axis at the deflection regionresulting from application of the axial force.
 3. The method of claim 2,wherein resisting axial compression comprises urging deflection of thesheath laterally relative to the longitudinal axis of the sheath.
 4. Themethod of claim 1, further comprising deforming the shapeable region toa substantially straightened configuration to facilitate movement of thesheath through vasculature, and resuming the shapeable region to thepre-established shape when unconstrained by the vasculature.
 5. Themethod of claim 1, wherein imparting the pre-established shape comprisesadvancing a member through a lumen of the sheath and into the shapeableregion, a distal region of the member assuming the pre-established shapewhen advanced into the shapeable region.
 6. The method of claim 1,wherein the shapeable region comprises a pre-formed outer portion of thesheath.
 7. The method of claim 1, wherein the shapeable region comprisesa pre-formed outer member secured to the sheath.
 8. The method of claim1, wherein the pre-established shape of the shapeable region is impartedby a stylet having a pre-determined shape.
 9. The method of claim 1,further comprising applying the axial force at the anchor region tocause a change in a bend angle at the deflection region while thepre-established shape of the shapeable region is substantiallymaintained.
 10. The method of claim 1, wherein applying the axial forcecomprises applying the axial force in a direction offset relative to thelongitudinal axis of the sheath.
 11. The method of claim 1, wherein thesheath further comprises a steering ribbon extending at least from theproximal region to the deflection region of the sheath, the steeringribbon having a width sufficient to contact an inner surface of thesheath at two diametrically opposite locations of the inner surface ofthe sheath, and wherein the steering ribbon separates a first steeringtendon from a second steering tendon of the one or more steeringtendons.
 12. The method of claim 11, further comprising steering thedistal end of the sheath in two directional planes, wherein respectivedeflection planes of the compression cage and the steering ribbon arealigned to maintain steering uniformity.
 13. The method of claim 1,wherein the anchor band includes a main cylindrical portion and aplurality of spaced annular rings.
 14. The method of claim 13, furthercomprising: inserting an introducer into a selected cardiac location;guiding the sheath through the introducer; and extending the shapeableregion of the sheath beyond a distal end of the introducer therebyallowing the shapeable region to assume the pre-established shape. 15.The method of claim 1, wherein the proximal region is maintained inshape during deflection of the deflection region.
 16. The method ofclaim 15, wherein sensing cardiac signals comprises mapping cardiactissue.
 17. The method of claim 1, further comprising delivering energyfrom the shapeable region of the sheath.
 18. The method of claim 17,wherein delivering energy comprises delivering energy sufficient toablate cardiac tissue.